Thread generating machine



Feb- 3, 19 9 K. H. SCHULTZE I 2,871,634

' THREAD GENERATING MACHINE Filed May 22. 1956 3 Sheets-Sheet 1 5 L a 2 E 4 1t 14 1i ,3 76' 1 g #4 H 13 1E 76 Kuff. H. JC/Iu/fZe Inventor."

ATTLRNEY Feb; 3, 1959 H. scHu z 2,871,634

THREAD GENERATING MACHINE Filed May 22, 1956 3 Sheets-Sheet 2 Feb. 3, 1959 K. H. SCHULTZE I 2,871,634

THREAD GENERATING MACHINE Filed May 22, 1956 3 Sheets-Sheet 3 Pg. 43 42 #7 ii Kur/ H. c/lu/fze Inventor? ATO Y United States Patent "ice THREAD GENERATING MACHINE Kurt H. Schultze, Berlin-Frohnau, Germany, assignor to Herbert Lindner G. in. b. H., Berlin-Wittenau, Germany, a corporation of Germany Application May 22, 1956, Serial No. 586,424

Claims priority, application Germany June 2, 1955 4 Claims. (Cl. 51-232) My invention relates to thread generating machines such as thread grinding machines which include a guide screw and more particularly to machines of that type which comprise an adjustable rapid traverse for a quick return of the work spindle and wherein said work spindle and said guide screw are connected by change gears which effect the return movement of the work piece support such as work piece slide.

1n the known machines of that type the work piece support was returned by rapid traverse to its starting position as soon as the tool passed the length of the threaded portion of the workpiece and thus has completed its machining operation. As the workpiece support is being moved by the guide or feed screw connected by change gears with the workpiece spindle, the speed r .tic between guide screw and workpiece spindle was changed in agreement with the pitch or lead of the screw to be generated. Therefore, a constant rapid return traverse of the workpiece support, though desirable, was not achieved even when the workpiece spindle turned at high constant speed, the speed of said support having been either too low or too high. Neither was it feasible to disconnect, i

exceeded even at the steepest pitch or lead being content with accordingly low speeds of the support at gentler pitches or leads.

It is an object of my invention to avoid the said dis advantages and to provide a'thread generating machine in which the workpiece support always returns to its starting position with the highest admissible return speed without necessitating even a temporary disengagement of the change gears mounted between the work spindle and the guide or feed screw, and in which the return speed will not rise in case of an inadvertent wrong setting of the machine thereby protecting the same against damage.

In accordance with my invention I use two mutually independent regulators for the control of the speed of the workpiece spindle, said regulators determining respectively the working or operational speed and the rapid reverse speedof the workpiece spindle, one of said regulators being selectively switchable as regulator for the workpiece spindle motor while the other regulator is disconnected; the regulator for therapid reverse speed of the work spindle having switch positions in accordance with the pitch of the thread to be generated and thus providing the workpiece spindle with rapid reverse speeds I which will give to the guide'screw an approximately constant return speed at all ratios of the change gear, which 2,871,634 Patented Feb. 3, 1959 ratios correspond to the pitches of the threads tobe "generated, thereby imparting an approximately constant return speed to the workpiece support independent of the actually used operational working speed of the work'- piece spindle.

The said and other objects of my invention will be more fully understood from the following specification when read with the accompanying drawing in which one embodiment is illustrated.

In the drawing:

Fig. 1 shows diagrammatically an extended view of the gearing arrangement of a thread generating machine, Fig. 2 an electric circuit diagram relating thereto,

Fig. 3 a front view of the switchboard for said electric circuit, and

Fig. 4 an axial sectionof the centrifugal governor attached to the guide or feed screw of the machine.

The same reference numerals indicate the same or equivalent parts in all figures of the drawing.

The guide or feed screw 2 is mounted rotatably, but not displacezble in i ts axial direction, in the workpiece saute-rt, for examplein the slide 1 of the machine'tool and. engages the nut 4 secured to the machine frame 3. The, workpiece spindle 7, which is rotatably mounted upon the slidable work piece support 1, is driven by an electric variable-speed motor 5 over a gearing assembly 6 and between said workpiece spindle 7 and the guide screw 2 is a change gear 8 which permits adjustment of the ratio between the pitch or lead of the screw to be ncrtted and the guide screw. The said gearing assem- J y 6 comprises two shafts 9 and 9 of which shaft 9 connected over the worm gear 10, 11 to the electro- 1 gnetic working speed coupling 12 and shaft 9 over bevel gears 13 and spur wheels 14, 15 to the electromagfitic high ll1VIS3 speed coupling 16. The couplings 12 and i6 w?.ich are controlled by relay switches 63 and 64, rzspectively, work upon the common shaft 17 connectin th:- s me either to shaft 9 or to shaft 9 The shaft drives over the worm gear 18, 19 the work spindle '7, 1d. the same will be driven at lower or higher speed is at the operational or working speed and the reverse 3 eed, respectively, depending whether the coupling'lz the coupling 16 is engaging. Spur wheels 20, 21 are needed between the workpiece spindle 7 and the shaft '3 of the said change gear 8,

The variable-speed motor 5 driving the workpiece s indle 7 is adjustable within a range of about 1:4 and areferably crnstructed as a D. C. motor with field regua .ali n. Such field regulation is effected as illustrated in Fig. 2 by the mutually independent and alternately operatin regulators 25 and 27 located in parallel conduits 6E) and 6t, res ectively, within the circuit of the field inding 62 of the motor 5. A switch board 23 mounted an the machine frame 3 is providedwith a rotary grip 24 actuating the regulator 25, situated in rear thereof, for regulatng the working speed of the work spindle 7, nd a rotary grip 26 actuating the regulator 27, situated in the rear thereof, for regulating the fast reverse speed cf the workpiece spindle 7 in dependence of the generated pitch or lead of the screw but indenendentof the rotational working speed of spindle 7. Between the said grips 24, 26 is a speedometer 28 indicating the number of revolutions per minute of the workpiece spindle 7. The said switch board 23 also contains press keys or the like 29, 3d, 31 each actuating one relay,

namely key 29, the relay 63 to start the working operation, key 30 the relay 64 for the rapid traverse; and key 31 the switch shutt ng ed the driving motor 5.

which in an outer row indicates the setting position for cach'of diflerent screw pitches or leads to be gen?- erated, for example, as illustrated in Fig. 3, twelve such positions for pitches between 1 mm. and 12 mm. The inner row of said scale 34 indicates the coordinated rotational speed of the workpiece spindle 7 ranging from 60 to 15 R. P. M. and readable on the speedometer 28. The said rotational speeds conform to an approximately constant traverse or rapid return speed of the guide screw 2 over the entire setting range equivalent to a return speed of about 2 meters per minute of the workpiece support such as the grinding slide 1.

The guide or feed screw 2 is connected with the centrifugal governor 32 by a clutch for example a pin clutch 33 as shown schematically in Fig. 1 and in detail in Fig. 4. The guide screw 2 being driven by the change gear 8 rotates in a bearing 35 attached to the governor casing 42. The clutch 33 comprises a driving disc 38 which is keyed upon shaft 39 mounted in said casing 42 and is provided with a pin 37 adapted to engage a radial groove 36 in the end face of guide screw 2. A countershaft 41, rotatably mounted in the casing 42, has keyed upon it a smaller pinion 43 and a larger pinion 44 which engage, respectively, a larger pinion 40 keyed upon said shaft 39 and a smaller pinion 45 keyed upon an end shaft 46 which is also rotatably mounted in said casing 42, and supports the sensitive parts of the centrifugal governor 32. Shaft 46 thus rotates at higher speed than the guide screw 2 thereby increasing the sensitivity of the governor 32.

On a flange 47 secured to the cover 48 of the casing 42 are mounted two semi-circular contact or slip sheets 49, 50 which are separated between both their ends by a gap 51. A disc 52 rotating with said end shaft 46 supports upon intermediate distancing sleeves 53 three one-armed and electrically conductive swing levers 54 in triangular arrangement each lever being provided 1 at its outer end with a contact brush 55 and a weight 56.

A circular or spiral spring 57 surrounds said brushes 55 and holds the same in contact with said contact sheets 49, 50 against arising centrifugal forces. The said three swing levers 54 with brushes 55 are electrically connected over a contact ring 58 and strands 59 soldered thereto. The triangular location of the brushes 55 and the paired arrangement of the semi-circular contact sheets 49, 50 insure an electric circuit as long as the said brushes are not lifted from said contact sheets by an excessive centrifugal force.

Pig. 2 shows the regulators 25 and 27 of the variablespeed motor being located in parallel conduits 60 and 61, respectively, within the circuit of the field winding 62 of the said motor. The same is switched in by the relay switch 63 for the working operation or by the relay switch 64 for the quick traverse operation, said relay switches 63, 64 being actuated by the press keys 29, 30, respectively, as described above. The relay switch 63 includes contacts 63 63 63 63 63 63 their association being indicated by the dotted line 63a, and the relay switch 64 includes contacts 64 64 64 64 64- 64 their association being indicated by the dotted line 64a. The press key 29 operates the auxiliary contact 29 and 29 shown on dotted line 29a and the press key 30 the auxiliary contacts 30 and 30 shown on dotted line 39a. The centrifugal governor 32 and the guide screw 2 are also schematically shown in Fig. 2.

My device operates as follows:

If the press key 29 for the working operation of the machine is depressed the auxiliary contact 29 will be closed and the auxiliary contact 29 opened. Thereby the relay switch 63 for the working operation of the machine will be switched in and the associated contacts shown on dotted line 63a will be actuated as follows: The contact 63 will be opened and thereby the relay switch 64 for the rapid traverse disconnected. The contact 63 will be closed and thereby a holding current for relay 63 initiated. The contact 63 will be opened thereby disconnectiug'regulator 27 for rapid-traverse'from conduit 61.

Thereafter only the regulator 25 controlling the opera tional working speed of the motor remains switched in. The contacts 63 63 and 63 are closed and switch in the motor 5. When the press key 31 is depressed the current between the circuits I and II will be interrupted and the holding contact 63 and relay switch 63 will drop If now the press key 30 for rapid traverse is depressed contact 30 opens, contact 30 closed and the relay switch 64 attracts and interrupts the circuit for the relay switch 63 by opening the contact 64 Simultaneously the contact 64 for the holding circuit of relay 64 is being closed. The contact 64 within conduit 60 of the regulator 25 for the operational working speed will be opened and the regulator 27 for rapid-transfer will alone determine the speed of motor 5. In addition contacts 64 64 and 64 are also closed thereby switching in the motor 5 to turn at thehigher speed for rapid return traverse which speed is set in dependence of the pitch or lead of the generated screw and is approximately constant for the enire switch range of regulator 27 being independent of the actually set working speed.

Should inadvertently the regulator 27 operated by the rotary grip 26 be set for a smaller pitch or lead than that being actually generated, then the guide screw 2 will be rotated at a speed which is higher than the approximately constant return speed whereby the centrifugal governor 32 having been adjusted to said constant return speed will become active. and distance the contact brushes 55 from the contact segments 49, 50, thus momentarily stopping the driving motor 5.

Having shown and described in detail one specific embodiment of my invention to illustrate the application of the principles of my invention, it will be well understood that the same may be otherwise embodied without departing from such principles and without avoiding the scope of the appended claims.

What I claim as my invention is:

1. In a thread generating machine the improvement comprising a slidable workpiece support; a feed screw for said support mounted rotatably but axially unshiftably therein; stationary threaded means receiving said feed screw to cause an axial displacement thereof together with the workpiece support during the rotation of said screw; a workpiece spindle rotatably mounted in said support; and an adjustable change gear operatively connecting said feed screw and said spindle; said change gear adapted to vary the ratio of the rotations of the feed screw and the workpiece spindle in accordance with the pitch of the thread to be generated upon the workpiece; an electric variable speed motor driving said workpiece spindle; a first and a second regulator to vary the speed of said motor; said regulators operating alternately and independently of each other; the first regulator controlling and setting the operational or working speeds of said workpiece spindle; and the second regulator controlling the higher reverse speeds of said spindle and setting such reverse speed in such dependence from the pitch of the actually generated thread that the highest admissible return speed of the feed screw and thus of the workpiece support results, such highest admissible return speed being at least approximately constant for any pitch of generated threads and indicator means associated with the second regulator, said indicator means defining setting positions for specific return speeds of the feed screw in dependence from the pitches of threads to be generated.

2. In a thread generating machine as defined in claim 1 a centrifugal governor rotating with the feed screw and adapted to switch off the said motor if the admissible return speed of said screw is exceeded.

3. In a thread generating machine as defined in claim 1 a centrifugal governor, a transmission gear between said feed 'screw and said governor rotating the same at higher speed, said governor being adapted to switch off the said motor if the admissible return speed of the screw is exceeded.

4. In a thread generating machine the improvement comprising a slidable workpiece support; a feed screw for said support mounted rotatably but axially unshiftably therein; stationary threaded means receiving said feed screw to cause an axial displacement thereof together with the workpiece support during the rotation of said screw; a workpiece spindle rotatably mounted in said support; an adjustable change gear operatively connecting said feed screw and said spindle; said change gear adapted to vary the ratio of the rotations of the feed screw and the workpiece spindle in accordance with the pitch of the thread to be generated upon the workpiece; an electric variable speed motor driving said workpiece spindle; a gearing including clutch means between said motor and said workpiece spindle driving the latter selectively at lower working speeds and higher reverse speeds, respectively; a first and a second regulator to vary the speed of said motor; said regulators operating alternately and independently of each other; the first regulator controlling and setting the operational or working speeds of said workpiece spindle; the second regulator con trolling the higher reverse speeds of said spindle and setting such reverse speed in such dependence from the pitch of the actually generated thread that the highest admissible return speed of the feed screw and thus of the workpiece support results, such highest admissible return speed being, at least approximately constant for any pitch of generated threads; and indicator means associated with the second regulator, said indicator means defining setting positions for specific return speeds of the feed screw in dependence from the pitches of threads to be generated.

References Cited in the file of this patent UNITED STATES FATENTS 1,901,926 Olson Mar. 21, 1933 2,169,159 Moller Aug. 8, 1939 2,363,559 Selnes Nov. 28, 1944 2,513,694 Turrettini July 5, 1950 

